The quality and safety of many temperature-sensitive perishable products can be compromised by improper temperature control during processing, distribution, and storage. International governmental agencies have become increasingly active in safeguarding consumers of perishable products by the passage of various food and drug regulations. A number of these regulations deal with monitoring the exposures of temperature-sensitive products during the different phases of the products' life, from the time of manufacture to the ultimate consumption of the goods. In the U.S. regulations are pending that require storage of fresh meat and poultry below 4.4.degree. C. (40.degree. F.), and fresh eggs below 7.2.degree. C. (45.degree. F.), EEC directive 93/43 has established maximum storage temperature conditions for fish, processed foods, pasteurized dairy products, and frozen foods.
In response to the increase in regulations and to the increase in consumer awareness of the possible consequences of poor temperature control, some food processing companies, trucking companies, and supermarket chains have begun utilizing the HACCP (Hazard Analysis Critical Control Point) Systems approach to food safety. This program involves hazard analysis, identification of critical control points, determination of the critical limits at those points, methods to routinely monitor those limits during commercial activities, corrective action procedures, appropriate record keeping and verification procedures. One of the critical control points is temperature monitoring during the different times in a product's life. Such monitoring programs involve measuring temperatures in processing and storage locations, in trucks, on loading/unloading docks, and on retail shelves. Chart recorders and electronic data loggers can be used to produce records that show compliance within the required storage temperature range. However, such monitoring methods suffer because they can only monitor the area where the probe is located. Even if several probes are used, this provides only a one point in time or "snapshot" of the true temperature distribution. It is also well known that temperatures within warehouses, trucks, and retail refrigeration units can vary widely even when the items are in close proximity to each other. These differences can be due to poor air circulation, improper stacking of products in the cooler/freezer, or malfunctioning refrigeration equipment. Relying on temperature recorders or probes is also inadequate because the temperature monitoring equipment does not follow the product to the ultimate consumer, where additional abuse may occur.
In addition to the recording devices described above, instantaneous temperature measurements can be made with a thermometer or other suitable temperature indicating instrument. It is not practical to routinely make these measurements on a "spot check" basis on individual packages because of the time involved in making the measurements and the possible alteration of the product due to making the measurement, e.g., piercing a package of ground beef with a temperature probe. Instantaneous temperature indicators could also be attached to products when they are manufactured. These indicators would be useful in determining if a critical temperature has been exceeded but would not give an indication of the extent or length of time to which a product is exposed above a given temperature. This is important because, while for example a product may still be usable if exposed at a temperature of say 30.degree. C. (86.degree. F.) for up to several hours, this same product would be completely unusable and should be discarded when exposed to that temperature level for any appreciable length of time in excess of six hours.
The U.S. Government has required by law that proper handling and cooking directions be printed on labels applied to individual packages of fresh meat, poultry, and fish products to warn the consumer about the potential hazardous nature of the of those products and to give directions regarding proper temperature storage conditions. The device of this invention allows the signaling of a temperature abuse condition when the indicator label is attached to a perishable product.